Detection and mitigation of interference based on interference location

ABSTRACT

Embodiments include a novel receiver architecture to optimize receiver performance in the presence of interference. In various embodiments, the presence of interference is detected, and the relative frequency location of the interference is detected. The relative frequency location specifies whether the frequency of the interference is high side (above the desired signal, i.e., at a higher frequency) or low side (below the desired signal). The receiver is configured based on the detected interference and relative location thereof. For a device such as a cellular phone that operates in a dynamic and changing environment where interference is variable, embodiments advantageously provide the capability to modify the receiver&#39;s operational state depending on the interference.

RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 13/540,116 titled “Detection and Mitigation of InterferenceBased on Interference Location” filed Jul. 2, 2012, now U.S. Pat. No.8,761,702, the entirety of which is incorporated by reference herein.

FIELD

The present disclosure relates to receiver architectures in acommunications system, and more particularly, some embodiments relate tomethods and apparatuses for detecting and mitigating interference andoptimizing receiver performance.

BACKGROUND

Radio frequency transceivers in cellular systems commonly receive anddecode a desired signal in the presence of interference, which hascommonly required a compromise in receiver performance. For example, inorder to prevent clipping due to interference, several stages of narrowanalog filters are typically found in conventional receiver designs.Such filters add current drain and distort the desired signal, thusdegrading receiver performance. Additionally, the active stages of thereceiver, particularly the radio frequency (RF) stages, are designedwith high levels of linearity so that distortion is minimized in thepresence of interference. This linearity often requires relatively highbias conditions and therefore requires relatively high current drain.

A typical prior art receiver architecture is shown in FIG. 1. Thisarchitecture represents a typical receiver implementation and isdescribed in U.S. Pat. No. 6,498,926 to Ciccarelli et al. Withinreceiver 100, the transmitted RF signal is received by antenna 112,routed through duplexer 114, and provided to low noise amplifier (LNA)116, which amplifies the RF signal and provides the signal to bandpassfilter 118. Bandpass filter 118 filters the signal to remove some of thespurious signals which can cause intermodulation products in thesubsequent stages. The filtered signal is provided to mixer 120, whichdownconverts the signal to an intermediate frequency (IF) with asinusoidal signal from local oscillator 122. The IF signal is providedto bandpass filter 124, which filters spurious signals anddownconversion products prior to the subsequent downconversion stage.The filtered IF signal is provided to variable gain amplifier (VGA) 126,which amplifies the signal with a variable gain to provide an IF signalat the required amplitude. The gain is controlled by a control signalfrom AGC control circuit 128. The IF signal is provided to demodulator130, which demodulates the signal in accordance with the modulationformat used at the transmitter (not shown).

For this prior art architecture, the local oscillator signal (LO) iseither tuned to match the radio frequency signal (RF), so that thereceived signal is converted directly to baseband, or it is tuned toconvert the received RF signal to some much lower intermediate frequency(IF) for further filtering. At baseband or IF, the filters are set tothe bandwidth of the particular RF system to receive the desired signaland remove interference.

The architecture in FIG. 1 is designed to receive the desired signal inthe presence of interference. The filter at baseband or IF is set toremove completely any interference, and the RF stage gain and bias areset to receive the signal with interference with minimal distortion.Thus, such a conventional system makes assumptions about the presence ofinterference, which may reduce interference at the expense of receiverperformance when the expected interference is present, but which mayconstitute a wasteful approach when such assumptions are incorrect.

Another prior art receiver architecture is disclosed at U.S. Pat. No.6,498,926 to Ciccarelli et al. In this prior art architecture,post-demodulation quality is used to set the bias conditions andtherefore the linearity of the RF circuits. This prior art approach doesnot address the problem fully because the receiver state is adjustedbased only on the baseband data quality measurement, which might bedegraded for numerous reasons and not just due to interference and/orreduced RF linearity. Also, this architecture does not do anything toreduce the filtering requirement to match the actual interferenceconditions.

Another prior art receiver architecture is disclosed at U.S. Pat. No.6,670,901 to Brueske et al. This prior art architecture includes anon-channel power detector, a wide band power detector, and anoff-channel power detector. The wideband detector and off-channeldetector will indicate if high levels of interference are present andallow adjustment of the receiver bias based on that. This prior artarchitecture suggests using the information from these power detectorsto adjust the dynamic range of several blocks (LNA, mixer, filter,analog-to-digital (A/D) converter, and digital filter). By adjusting thedynamic range and/or bias of these stages, the current drain can beoptimized. However, this prior art approach uses wideband detectionwithout selectivity and therefore is unable to distinguish out-of-bandinterference, i.e., interference that is several channels away, fromnearby interference in the adjacent or nearby channels. Therefore, thearchitecture cannot fully optimize the performance of the receiver.

Since an actual device such as a cellular phone operates in a dynamicand changing environment where interference is variable, it is desirableto be able to modify the receiver's operational state depending on theinterference.

SUMMARY

In some embodiments of the present disclosure, an apparatus includes anamplifier configured to amplify an input signal. A local oscillator isconfigured to generate an oscillator signal. A mixer is coupled to theamplifier and is configured to mix the amplified input signal outputtedby the amplifier with the oscillator signal. A baseband filter isconfigured to filter an output of the mixer to pass a selected band offrequencies. An interference frequency detection (IFD) module is coupledto an output of the baseband filter directly or via one or moreintermediate components. The IFD module is configured to detect arelative frequency location of an interference signal, and to provide anIFD output signal indicative of the detection result. A state machine iscoupled to an output of the first baseband filter directly or via or onemore intermediate components. The state machine is further coupled tothe IFD module and to the local oscillator. The state machine isconfigured to provide a feedback signal to the local oscillator, basedon the IFD output signal, to cause the local oscillator to update theoscillator signal so that the amplified input signal, when mixed withthe updated oscillator signal, is not located at a frequency band of theinterference signal.

In some embodiments, an apparatus includes a first processing module anda second processing module configured to receive a first input signaland a second input signal, respectively. Each processing module includesan amplifier configured to amplify the input signal of that processingmodule, a local oscillator configured to generate an oscillator signal,a mixer coupled to the amplifier and configured to mix the amplifiedinput signal outputted by the amplifier with the oscillator signal, anda baseband filter configured to filter an output of the mixer to pass aband of frequencies. A logic module is coupled to the first and secondprocessing modules. The logic module includes an interference frequencydetection (IFD) module coupled to an output of the baseband filter ofthe second processing module directly or via one or more intermediatecomponents. The IFD module is configured to detect whether aninterference signal is at a higher frequency or a lower frequency thanan output of the baseband filter of the second processing module, and toprovide an IFD output signal indicative of the detection result. Thelogic module also includes a state machine coupled to the IFD module andto the local oscillator of the first processing module. The statemachine is configured to provide a feedback signal to the localoscillator of the first processing module, based on the IFD outputsignal, to cause the local oscillator of the first processing module toupdate the corresponding oscillator signal so that the amplified inputsignal of the first processing module, when mixed with the updatedoscillator signal, is not located at a frequency band of theinterference signal.

In some embodiments, an input signal is amplified to provide anamplified input signal. An oscillator signal is generated. The amplifiedinput signal is mixed with the oscillator signal, to provide a mixedsignal. The mixed signal is filtered to pass a band of frequencies, toprovide a filtered signal. Based on the filtered signal, a relativefrequency location of an interference signal is detected. The detectedfrequency location of the interference signal may be relative to adesired signal for reception. A feedback signal is generated based onthe detected relative frequency location. The oscillator signal isupdated based on the feedback signal so that the amplified input signal,when mixed with the updated oscillator signal, is not located at afrequency band of the interference signal.

In some embodiments, first and second input signals are received from afirst antenna and a second antenna, respectively. The first and secondinput signals are amplified to provide first and second amplified inputsignals, respectively. First and second oscillator signals aregenerated. The first and second amplified input signals are mixed withthe first and second oscillator signals, respectively, to provide firstand second mixed signals. The first and second mixed signals arefiltered to pass a band of frequencies, to provide first and secondfiltered signals, respectively. Based on the second filtered signal, arelative frequency location of an interference signal is detected. Afeedback signal is generated based on the detected relative frequencylocation. The first oscillator signal is updated based on the feedbacksignal so that the first amplified input signal, when mixed with theupdated first oscillator signal, is not located at a frequency band ofthe interference signal.

BRIEF DESCRIPTION OF THE DRAWINGS

The following will be apparent from elements of the figures, which areprovided for illustrative purposes and are not necessarily to scale.

FIG. 1 is a block diagram of a receiver architecture known in the priorart.

FIG. 2 is a block diagram of a system architecture in accordance withsome embodiments of the present disclosure.

FIG. 3 is an illustration of interference frequency detection usingcomplex mixing in accordance with some embodiments.

FIG. 4 is an illustration of interference frequency detection using afast Fourier transform (FFT) in accordance with some embodiments.

FIGS. 5A-C are illustrations of receiver configurations in someembodiments.

FIGS. 6A-B are illustrations of interference in low intermediatefrequency (LIF) modes.

FIG. 7 is a block diagram of a multiple input multiple output (MIMO)receiver architecture in accordance with some embodiments.

FIG. 8 is a flow diagram of a process in accordance with someembodiments.

FIG. 9 is a flow diagram of a process in accordance with someembodiments.

DETAILED DESCRIPTION

This description of the exemplary embodiments is intended to be read inconnection with the accompanying drawings, which are to be consideredpart of the entire written description.

Embodiments of the present disclosure provide a novel receiverarchitecture to optimize receiver performance in the presence ofinterference. In various embodiments, interference frequency detectionmethods are used to determine the exact nature of the interference andto optimize the performance correspondingly. Also, the actual method ofoptimizing the receiver performance is novel compared to the prior artin that the frequency of operation is optimized based on the nature ofthe interference as determined by frequency detection measurements.

FIG. 2 is a block diagram of a system architecture of a receiver 200 inaccordance with some embodiments of the present disclosure. An inputsignal 202 is received, e.g., from an antenna. The input signal is shownin differential form (RF_RX+ and RF_RX−); other signals in FIG. 2 may bein differential form but are not labeled as such, for visual clarity andto reduce clutter. The input signal is amplified by a low noiseamplifier (LNA) 204 to provide an amplified input signal 214. A localoscillator 210 generates one or more oscillator signals 212 (e.g.,sinusoids) based on signals 208 from a synthesizer 206. A mixer 216mixes the amplified input signal 214 with the oscillator signal 212. Themixer may include in-phase and quadrature channels 216 a and 216 b.Separate processing pathways are shown in FIG. 2 for the in-phase andquadrature components (with similar reference characters but differentsuffixes, “a” or “b”), but the processing is similar for each, so thediscussion below focuses on the top pathway in FIG. 2, which may be anin-phase or quadrature path. It is to be understood that the variousfeedback effects from state machine 254 to components such as filtersand amplifiers may apply to components in either the in-phase orquadrature path.

Mixed signal 218 a provided by mixer 216 is processed by a series offilters 222 a, 232 a, 242 a, which may be baseband filters. Thesefilters implement the overall interference rejection of the baseband,and they may have programmable bandwidths with many different settings.For example, a multimode receiver may have bandwidths from 100 kHz up to10 MHz to support various modes like Global System for Mobilecommunications (GSM), Time Division-Synchronous Code Division MultipleAccess (TD-SCDMA), Wideband Code Division Multiple Access (WCDMA), LongTerm Evolution (LTE), and other communication standards as is known inthe art. Also, the filters provide progressively more rejection asprocessing moves further toward the output (toward the right side ofFIG. 2). Gain adjustment may be provided by a post-mixer amplifier (PMA)226 a and variable gain amplifier (VGA) 246 a.

An interference frequency detection (IFD) module 290 may be coupled toone or more outputs of VGA 246 a. IFD module 290 detects if interferenceis present and may detect whether the frequency of the interference ison the high side (above the desired signal to be received, i.e., at ahigher frequency) or on the low side (below the desired signal to bereceived, i.e., at a lower frequency). The term “desired signal” refersto the signal transmitted by the transmitter and which, ideally, thereceiver decodes. Details of IFD module 290 are provided further below.

Thus, mixed signal 218 a is filtered by filter 222 a to provide signal224 a, which is amplified to provide signal 228 a. The amplified signal228 a is filtered to provide signal 234 a and then filtered to providesignal 244 a, which is amplified to provide signal 248 a. A logic module250 includes a received signal strength indication (RSSI) module 252,which measures power and provides an output 253 to an RF interferencemitigation state machine 254. RSSI 252 is described further below. Statemachine 254 receives inputs from IFD module 290 and from RSSI 252, andprovides feedback to LNA 204, synthesizer 206, mixer 216, PMA 226 a(and/or 226 b), and VGA 246 a (and/or 246 b). Feedback is provided tocomponents in both the in-phase and quadrature processing pathways.State machine 254 may also provide signals 260 c, 260 b, and/or 260 a tofilters 222, 232, and/or 242 to enable one or more of the filters to beenabled. Logic module 250 may be coupled to a transmitter (not shown),which may provide a signal to an antenna for transmission.

State machine 254, which may be a digital state machine that may beimplemented in various ways, controls circuitry in receiver 200 toperform RSSI measurements, determine the optimum configuration for theRF circuits, and provide feedback accordingly. State machine 254 mayprovide feedback via signal 260 h to vary the gain of VGA 246 a and/or246 b. The gain change may offset any gain changes in the LNA 204, mixer216, and/or PMA 226 a and/or 226 b effected by state machine 254 throughsignals 260 e, 260 f, or 260 g. A gain change in the VGA 246 a willgenerally not improve the linearity of the receiver with interferencesince this VGA stage is after all the filter stages. However, if thegain of the LNA, mixer, and/or PMA is changed in order to improve thelinearity, the gain of the VGA may be adjusted to compensate for thereduction of gain in those stages.

One implementation of IFD module 290 is shown in FIG. 3. Thisimplementation uses complex mixers 310 a, 310 b to shift the receivedbaseband signal by a specified offset (e.g., the adjacent channeloffset) in the positive and negative directions. After low passfiltering at filters 315 a, 315 b, power detection is performed on theresultant signal using power estimation circuits 320 a, 320 b, which maybe implemented as peak detectors, power detectors, or as any other kindof power estimation circuit. So for the case shown in FIG. 3, the PdetHigh Side power is greater than the Pdet Low Side power (as determinedby a comparator 350), indicating that the frequency of the interference340 is on the high side relative to desired signal 330. While thisdetection is shown for the adjacent (denoted “adj”) channel in aparticular communications implementation, this technique may be appliedfor other frequency offsets also. The processing for the IFD moduleshown in FIG. 3 may be applied to a baseband signal in the in-phase orquadrature path shown in FIG. 2.

Another implementation of IFD module 290 is shown in FIG. 4. A fastFourier transform (FFT) 410 is performed on the input to IFD module 290to detect the frequency of the interference. FFT processing is common inmultimode architectures that support standards such as TD-SCDMA and LTEand may also be used for interference detection. FFT module 410 may beimplemented in various ways as known in the art. By analyzing the FFTresults in frequency bins such as the adjacent channel bins 415 a(frequency bin for f=f_(adj)) and 415 b (frequency bin for f=−f_(adj)),some embodiments of the present disclosure determine if interference ispresent and whether that interference 440 is on the high side or lowside relative to desired signal 430.

The architecture described allows optimization of the receiverconfiguration depending on the presence of and the frequency ofinterference. For example, FIGS. 5A-C show three possible receiverconfigurations that may be used to receive a narrowband signal inaccordance with the GSM or EDGE standards.

The three configurations are: (1) Direct conversion (DCR) mode as shownin FIG. 5A; Low Intermediate Frequency (LIF) Mode with Low Side Offsetas shown in FIG. 5B; and Low Intermediate Frequency (LIF) Mode with HighSide Offset as shown in FIG. 5C. In FIG. 5A, interference signals 520 a,520 b are shown on either side of desired signal 510, which is locatedat zero frequency. In FIG. 5B, interference signal 540 is shown on thelow side of desired signal 530, which has a low side offset (i.e.,frequency offset such that the desired signal is located at a negativefrequency offset). In FIG. 5C, interference signal 560 is shown on thehigh side of desired signal 550, which has a high side offset (i.e.,frequency offset such that the desired signal is located at a positivefrequency offset).

In general, the LIF modes of FIGS. 5B and 5C are preferred over the DCRmode of FIG. 5A, because the LIF modes can reject the DC offsetimperfections in the RF circuits. However, the LIF modes may haveperformance issues in the presence of interference, as illustrated inFIGS. 6A-6B. LIF reception for high side interference (i.e.,interference at a positive frequency) is shown for both low side offset(FIG. 6A) and high side offset (FIG. 6B) scenarios. Additionally, theimage signal (an artifact of circuit imperfections present at thefrequency having the same magnitude but opposite sign) created by theinterference signal is also included in FIGS. 6A-6B. In FIG. 6A,interference 630 is shown on the high side (at a positive frequency),and the image 632 of the interference is located at the same frequencyas desired signal 620. The image is present due to imperfections in theRF circuits and can only be improved to a certain level. Because ofthis, it is desirable to operate using the high side offset as in FIG.6B, where the interference 650 is at a positive frequency, and the image652 of the interference does not interfere with the desired signal 640.

Therefore, if the interference frequency detection (IFD) module 290indicates that the interference is on the high side (relative to thedesired signal), then in some embodiments of the present disclosure,reception may be performed using Low Intermediate Frequency Mode withHigh Side Offset. If the interference is on the low side (relative tothe desired signal), then reception may be performed using LowIntermediate Frequency Mode with Low Side Offset. If interference ispresent on both low and high sides, then reception may be performedusing Direct Conversion Mode. As these modes correspond to variousfrequencies of the desired signal, the modes may be selected byappropriate generation of the oscillator signal 212 that feeds mixer216. For example, state machine 254 may send a signal 260 d tosynthesizer 206 to cause the appropriate oscillator signal to begenerated to configure the receiver in one of the modes. Thus, statemachine 254 selects the appropriate receiver mode based on the detectedpresence and relative location of interference as identified by IFDmodule 290.

The receiver architecture of FIG. 2 may also be implemented efficientlyfor a MIMO (multiple input multiple output) system as shown in FIG. 7.Because of the MIMO requirements for 3G and 4G cellular systems, adiversity receiver is often included in the RF and basebandarchitecture. This additional receiver is not needed for GSM/EDGE modeand therefore may be used to perform the interference frequencydetection described above. Based on this information, the mode of thereceiver(s) may be optimally configured based on the determinedinterference level and/or the frequency of the interference.

FIG. 7 shows a receiver module 710 b, which may receive an input from aprimary receive antenna 712 b, and a receiver module 710 a, which mayreceive an input from a diversity antenna 712 a. Processing in each ofthe receiver modules is similar to processing discussed above in thecontext of FIG. 2, and only certain differences from FIG. 2 arediscussed below. The diversity receiver module 710 a may be used forinterference frequency detection at interference frequency detectionmodule 790. State machine 754 may provide feedback signals as shown inFIG. 7.

The use of the diversity receiver in some embodiments to performinterference estimation in parallel provides several advantages. Oneadvantage is that the diversity receiver can be adjusted to anybandwidth option that is desired at any time in order to detectinterference. The primary receiver is tasked with receiving the desiredsignal and therefore the baseband filters have limited bandwidth duringthe desired reception slot to limit noise and interference. Thediversity receiver, when used for interference detection, has no suchlimitation, so the bandwidth can be increased as desired. Anotheradvantage is that the diversity receiver gain may be adjusted for thebest performance to check the interference without considering thedesired signal. The primary receiver must receive the desired signal andtherefore the gain control is set in that receiver to optimize the levelof that signal. The diversity receiver, when used for interferencedetection, is again not constrained by the need to receive the desiredsignal, and therefore the gain may be optimized to detect interference.

FIG. 8 is a flow diagram of a process in accordance with someembodiments. After process 800 begins, an input signal (e.g., signal202) is amplified (block 810), to provide an amplified input signal(e.g., signal 214). An oscillator signal (e.g., signal 202) is generated(block 820). The amplified input signal is mixed (block 830) with theoscillator signal, to provide a mixed signal (e.g., signal 218 a). Themixed signal is filtered (block 840) to pass a band of frequencies, toprovide a filtered signal (e.g., signal 224 a). Based on the filteredsignal, a relative frequency location of an interference signal isdetected (block 850). The detected frequency location of theinterference signal may be relative to a desired signal for reception. Afeedback signal (e.g., signal 260 d) is generated (block 860) based onthe detected relative frequency location. The oscillator signal isupdated (block 870) based on the feedback signal so that the amplifiedinput signal, when mixed with the updated oscillator signal, is notlocated at a frequency band of the interference signal.

In some embodiments, detecting the relative frequency location of theinterference signal may be based on complex mixing. The filtered signalmay be shifted, directly or after additional filtering or amplification,by a predetermined offset in a first direction, to provide a low sideshifted signal. The low side shifted signal may be low pass filtered, toprovide a low pass filtered low side signal. The power of the low passfiltered low side signal may be measured, to provide a low side powermeasurement. The filtered signal may be shifted, directly or afteradditional filtering or amplification, by the predetermined offset in asecond direction opposite the first direction, to provide a high sideshifted signal. The high side shifted signal may be low pass filtered,to provide a low pass filtered high side signal. The power of the lowpass filtered high side signal may be measured, to provide a high sidepower measurement. The low side power measurement, the high side powermeasurement, or both, may be compared to a predetermined threshold.

Updating the oscillator signal may cause the amplified input signal tobe shifted higher in frequency, when the high side power measurement isgreater than the predetermined threshold, may cause the amplified inputsignal to be shifted lower in frequency, when the low side powermeasurement is greater than the predetermined threshold, and may causethe amplified input signal to be shifted neither higher nor lower infrequency, when both the high side power measurement and the low sidepower measurement are greater than the predetermined threshold.

In some embodiments, detecting the relative frequency location of theinterference signal may be based on fast Fourier transform (FFT)processing. A FFT may be performed on the filtered signal, directly orafter additional filtering or amplification to provide a frequencydomain signal. A comparison may be made between a predeterminedthreshold and the frequency domain signal at a first frequency bin,corresponding to a predetermined frequency magnitude and a first sign(e.g., positive). A comparison may also be made between thepredetermined threshold and the frequency domain signal at a secondfrequency bin, corresponding to the predetermined frequency magnitudeand a second sign opposite the first sign (e.g., negative). Based on thecomparison, the relative location frequency location of the interferencesignal may be determined.

The amplified input signal may be shifted higher in frequency when thefrequency domain signal at the first frequency bin is greater than thepredetermined threshold, may be shifted lower in frequency when thefrequency domain signal at the second frequency bin is greater than thepredetermined threshold, and may shifted neither higher nor lower infrequency when the frequency domain signal at both the first and secondfrequency bins is greater than the predetermined threshold.

FIG. 9 is a flow diagram of a process in accordance with someembodiments. After process 900 begins, first and second input signalsare received (block 910) from a first antenna and a second antenna,respectively. The first and second input signals are amplified (block920) to provide first and second amplified input signals, respectively.First and second oscillator signals are generated (block 930). The firstand second amplified input signals are mixed (block 940) with the firstand second oscillator signals, respectively, to provide first and secondmixed signals. The first and second mixed signals are filtered (block950) to pass a band of frequencies, to provide first and second filteredsignals, respectively. Based on the second filtered signal, a relativefrequency location of an interference signal is detected (block 960). Afeedback signal is generated (block 970) based on the detected relativefrequency location. The first oscillator signal is updated (block 980)based on the feedback signal so that the first amplified input signal,when mixed with the updated first oscillator signal, is not located at afrequency band of the interference signal.

Although examples are illustrated and described herein, embodiments arenevertheless not limited to the details shown, since variousmodifications and structural changes may be made therein by those ofordinary skill within the scope and range of equivalents of the claims.

What is claimed is:
 1. An apparatus comprising: an interferencefrequency detection (IFD) module coupled to an output of a filterdirectly or via one or more intermediate components, the IFD moduleconfigured to: detect a relative frequency location of an interferencesignal, and provide, at an output of the IFD module, an IFD outputsignal indicative of the detection result; and a state machine coupledto the output of the IFD module, the state machine configured to providea feedback signal, based on the IFD output signal, for causing a shiftin energy in an input signal of the filter away from the detectedfrequency location.
 2. The apparatus of claim 1, wherein the IFD moduleincludes: a low side mixer configured to shift an input of the IFDmodule by a predetermined offset in a first direction; a first low passfilter configured to filter an output of the low side mixer; a low sidepower estimation circuit configured to measure power at an output of thefirst low pass filter; a high side mixer configured to shift the inputof the IFD module by the predetermined offset in a second directionopposite the first direction; a second low pass filter configured tofilter an output of the high side mixer; a high side power estimationcircuit configured to measure power at an output of the second low passfilter; and a comparator configured to output the IFD output signalbased on a comparison between a predetermined threshold and at least oneof an output of the low side power estimation circuit and an output ofthe high side power estimation circuit.
 3. The apparatus of claim 2,wherein the predetermined offset is a difference in frequencies betweenadjacent channels used for reception.
 4. The apparatus of claim 2,wherein the feedback signal is configured to cause the energy in theinput signal to be shifted higher in frequency, when the output of thehigh side power estimation circuit is greater than the predeterminedthreshold.
 5. The apparatus of claim 2, wherein the feedback signal isconfigured to cause the energy in the input signal to be shifted lowerin frequency, when the output of the low side power estimation circuitis greater than the predetermined threshold.
 6. The apparatus of claim2, wherein the feedback signal is configured to cause the energy in theinput signal neither to be shifted higher nor lower in frequency, whenthe respective outputs of the low side power estimation circuit and thehigh side power estimation circuit are greater than the predeterminedthreshold.
 7. The apparatus of claim 1, wherein the IFD module includes:a fast Fourier transform (FFT) module configured to perform a FFT on aninput of the IFD module; and a comparison module configured to outputthe IFD output signal based on a comparison between a predeterminedthreshold and at least one of an output of the FFT module at a firstfrequency bin, corresponding to a predetermined frequency magnitude anda first sign, and the output of the FFT module at a second frequencybin, corresponding to the predetermined frequency magnitude and a secondsign opposite the first sign.
 8. The apparatus of claim 7, wherein thepredetermined frequency magnitude corresponds to a difference infrequencies between adjacent channels used for reception.
 9. Theapparatus of claim 7, wherein the feedback signal is configured to causethe energy in the input signal to be shifted higher in frequency, whenthe output of the FFT module at the first frequency bin is greater thanthe predetermined threshold.
 10. The apparatus of claim 7, wherein thefeedback signal is configured to cause the energy in the input signal tobe shifted lower in frequency, when the output of the FFT module at thesecond frequency bin is greater than the predetermined threshold. 11.The apparatus of claim 7, wherein the feedback signal is configured tocause the energy in the input signal neither to be shifted higher norlower in frequency, when the respective outputs of the FFT module at thefirst and second frequency bins are greater than the predeterminedthreshold.
 12. An apparatus comprising: an interference frequencydetection (IFD) module coupled to a first processing module and to asecond processing module, wherein the first processing module isconfigured to receive a first signal from a first antenna and processthe first signal, and the second processing module is configured toreceive a second signal from a second antenna and process the secondsignal, wherein the IFD module is coupled to an output of a filter ofthe second processing module directly or via one or more intermediatecomponents, the IFD module configured to: detect whether an interferencesignal is at a higher frequency or a lower frequency than an output ofthe filter of the second processing module, and provide an IFD outputsignal indicative of the detection result; and a state machine coupledto the IFD module and to the first processing module, the state machineconfigured to provide a feedback signal, based on the IFD output signal,for causing a shift in energy in an input signal of a filter of thefirst processing module away from a frequency band of the interferencesignal.
 13. The apparatus of claim 12, wherein the IFD module includes:a low side mixer configured to shift an input of the IFD module by apredetermined offset in a first direction; a first low pass filterconfigured to filter an output of the low side mixer; a low side powerestimation circuit configured to measure power at an output of the firstlow pass filter; a high side mixer configured to shift the input of theIFD module by the predetermined offset in a second direction oppositethe first direction; a second low pass filter configured to filter anoutput of the high side mixer; a high side power estimation circuitconfigured to measure power at an output of the second low pass filter;and a comparator configured to output the IFD output signal based on acomparison between a predetermined threshold and at least one of anoutput of the low side power estimation circuit and an output of thehigh side power estimation circuit.
 14. The apparatus of claim 12,wherein the IFD module includes: a fast Fourier transform (FFT) moduleconfigured to perform a FFT on an input of the IFD module; and acomparison module configured to output the IFD output signal based on acomparison between a predetermined threshold and at least one of anoutput of the FFT module at a first frequency bin corresponding to apredetermined frequency magnitude and a first sign and the output of theFFT module at a second frequency bin corresponding to the predeterminedfrequency magnitude and a second sign opposite the first sign.
 15. Amethod comprising: filtering an input signal, to provide a filteredsignal; detecting, based on the filtered signal, a relative frequencylocation of an interference signal; generating a feedback signal basedon the detected relative frequency location, and updating an oscillatorsignal based on the feedback signal, to cause a shift in energy in theinput signal away from the detected frequency location.
 16. The methodof claim 15, wherein detecting the relative frequency location of theinterference signal includes: shifting the filtered signal, directly orafter additional filtering or amplification, by a predetermined offsetin a first direction, to provide a low side shifted signal; low passfiltering the low side shifted signal, to provide a low pass filteredlow side signal; measuring power of the low pass filtered low sidesignal, to provide a low side power measurement; shifting the filteredsignal, directly or after additional filtering or amplification, by thepredetermined offset in a second direction opposite the first direction,to provide a high side shifted signal; low pass filtering the high sideshifted signal, to provide a low pass filtered high side signal;measuring power of the low pass filtered high side signal, to provide ahigh side power measurement; and comparing a predetermined threshold andat least one of the low side power measurement and the high side powermeasurement.
 17. The method of claim 16, wherein updating the oscillatorsignal includes updating the oscillator signal to cause the input signalto be shifted higher in frequency, when the high side power measurementis greater than the predetermined threshold.
 18. The method of claim 16,wherein updating the oscillator signal includes updating the oscillatorsignal to cause the input signal to be shifted lower in frequency, whenthe low side power measurement is greater than the predeterminedthreshold.
 19. The method of claim 16, wherein updating the oscillatorsignal includes updating the oscillator signal to cause the input signalto be neither shifted higher nor lower in frequency, when the high sidepower measurement and the low side power measurement are greater thanthe predetermined threshold.
 20. The method of claim 15, whereindetecting the relative frequency location of the interference signalincludes: performing a fast Fourier transform (FFT) on the filteredsignal, directly or after additional filtering or amplification toprovide a frequency domain signal; comparing a predetermined thresholdand at least one of the frequency domain signal at a first frequencybin, corresponding to a predetermined frequency magnitude and a firstsign, and the frequency domain signal at a second frequency bin,corresponding to the predetermined frequency magnitude and a second signopposite the first sign.
 21. The method of claim 20, wherein thefeedback signal is configured to cause the updated oscillator signal,provided to a mixer, to shift the input signal higher in frequency, whenthe frequency domain signal at the first frequency bin is greater thanthe predetermined threshold.
 22. The method of claim 20, wherein thefeedback signal is configured to cause the updated oscillator signal,provided to a mixer, to shift the input signal lower in frequency, whenthe frequency domain signal at the second frequency bin is greater thanthe predetermined threshold.
 23. The method of claim 20, wherein thefeedback signal is configured to cause the updated oscillator signal,provided to a mixer, to neither shift the input signal higher nor lowerin frequency, when the frequency domain signal at the first and secondfrequency bins is greater than the predetermined threshold.
 24. A methodcomprising: receiving, at an interference frequency detection module, afirst signal, wherein the first signal is a result of processing asecond signal received from a first antenna; at the interferencefrequency detection module, detecting, based on the first signal, arelative frequency location of an interference signal; generating afeedback signal based on the detected relative frequency location, andupdating an oscillator signal based on the feedback signal, to cause ashift in energy in a third signal away from the detected frequencylocation, wherein the third signal is a result of processing a fourthsignal received from a second antenna.